Speaking after almost a week of refusing to comment on the leak but issuing four statements, Cameron said he and his wife, Samantha, held 5,000 units in the Blairmore Investment Trust for three years from 1997.

The stake was purchased for £12,497 and sold for £31,500 in January 2010, giving the Camerons a £19,003 profit, £300 below the capital gains tax allowance.

The prime minister insisted the family declared all annual dividends they received from the investment, and paid full income tax on any returns.

The revelation comes five days after the Tory leader’s father, Ian Cameron, was named in an unprecedented leak of more than 11m documents from Panamanian law firm Mossack Fonseca.

…

In an interview with ITV’s political editor, Robert Peston, on Thursday evening, the prime minister defended his father’s involvement in the fund.

“I want to be as clear as I can about the past, about the present, about the future, because, frankly, I don’t have anything to hide, I’m proud of my dad and what he did and the business he established and all the rest of it,” Cameron said.

“I can’t bear to see his name being dragged through the mud. I chose to take a different path from my father, grandfather and great-grandfather, who were all stockbrokers, and I’ve got nothing to hide in my arrangements and I’m very happy to answer questions about it.”

Cameron also rejected suggestions that the fund was created to shelter investors from tax. He said: “I think a lot of the criticisms are based on a fundamental misconception, which is that Blairmore Investment, a unit trust, was set up with the idea of avoiding tax. It wasn’t.

“It was set up after exchange controls went so that people who wanted to invest in dollar denominated shares and companies could do so.”